As demand for semiconductor devices increase the need for improved device inspection capabilities will also continue to increase. One technology commonly utilized in optical inspection methodologies includes the implementation of a photocathode. In a general sense, a photocathode emits photoelectrons in response to the absorption of photons impinging on the photocathode. One commonly implemented design includes the deposition of photocathode material on a supporting substrate surface having an index of refraction different than the photocathode material. A typical photocathode includes either a transmissive based photocathode or a reflective based photocathode. In a transmissive based photocathode, incident photons must travel through the substrate material before they impinge on the photocathode material. In a reflective based photocathode, incident photons travel through the active photocathode area and then reflect off of the substrate-cathode interface and travel back through the photocathode area prior to the emission of photoelectrons from the surface of the photocathode surface. Both the reflective and transmissive configurations lead to efficiency losses in the photon-photoelectron conversion process.
Therefore, it is desirable to create a photocathode and photocathode implementing systems that cure the defects of the prior art, thereby providing a photocathode optical architecture having improved efficiency characteristics relative to the prior art.